1.1-25%x=30 -0.25x=29 x=-116
2.1/4÷（3-5/13-8/15）
=1/4/(1+8/13+7/15)
=1/4/(1+120/195+91/195)
=1/4/(406/195)
=1/4*195/406
=195/1624
3.
197x97/98+1/98
=(196*97+97)/98+1/98
=196*97/98+97/98+1/98
=2*97+1
=194+1
=195
4.3又1/5-（0.2-6/7）
= 3又1/5-（1/5-6/7）
=3又1/5-1/5+6/7
=3又6/7
5.4-5/11×11+7/11×11
=4-5+7
=6